Effect of pupil dilation on the accuracy of the IOLMaster.

Purpose: To evaluate the effect of pupil dilation on the accuracy of the IOLMaster (Zeiss) in performing biometry and to assess test-retest variability without pupil dilation.

Setting: Ophthalmic outpatient department of a district general hospital.

Methods: This prospective study comprised consecutive patients presenting to a cataract clinic (study group) who had biometry performed with the IOLMaster before and after pupil dilation. A control group was recruited from consecutive patients attending a cataract preassessment clinic who had 2 sets of biometric measurements with the IOLMaster but without pupil dilation. The SRK/T formula was used to calculate intraocular lens (IOL) power.

Results: The IOLMaster showed excellent reproducibility in the control group with no significant test-retest variability between the 2 sets of readings. The study group showed a statistically significant change in K2 and average keratometry values (P <.05) but no significant change in axial length or IOL power between undilated and dilated pupil biometry readings. No systematic errors were revealed.

Conclusions: Dilating the pupil did not adversely affect the clinical accuracy of the IOLMaster.